Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $113.72   5.221%   $119.6573   $119.66   $119.65   $119.70  
  Purchase #2 $181.84   9.763%   $199.593   $199.59   $199.60   $199.60  
  Purchase #3 $196.73   5.706%   $207.9554   $207.96   $207.95   $208.00  
  Purchase #4 $168.33   11.343%   $187.4237   $187.42   $187.40   $187.40  
  Purchase #5 $7.46   10.697%   $8.258   $8.26   $8.25   $8.30  
  Purchase #6 $177.99   13.491%   $202.0026   $202.00   $202.00   $202.00  
  Purchase #7 $35.86   7.663%   $38.608   $38.61   $38.60   $38.60  
  7 purchase totals = $881.93       $963.4980   $963.50   $963.45   $963.60